Development and Validation of a UHPLC-MS/MS Method for the Analysis of Fusarium Mycotoxins in Onion

Fusarium basal rot (FBR) of onion is a serious disease problem worldwide. The Fusarium species causing FBR can also produce mycotoxins that are potentially harmful to humans and animals. In this study, a multiple reaction monitoring technique with ultra-high-performance liquid chromatography–tandem mass spectrometry (MRM UHPLC-MS/MS) was developed and validated for onion matrix to study Fusarium mycotoxins in the harvested onions. This study was focused on fumonisins B 1 , B 2 , and B 3 (FB 1 , FB 2 , and FB 3 ), beauvericin (BEA), and moniliformin (MON), which are the main mycotoxins produced by Fusarium oxysporum and Fusarium proliferatum . In the in-house validated protocol, the onion samples were extracted with methanol:water (3:1) using magnetic stirring for 15 min. FBs and BEA were determined directly from the filtered extracts, whereas MON required sample concentration prior to analysis. No cleanup of extracts was needed prior to analysis. The target mycotoxins were separated on an Acquity UPLC system BEH C18 column with gradient elution. Mycotoxins were identified and quantified using 13 C-FB 1 as internal standard. Minor matrix effect was compensated using multi-point matrix-matched calibration curves with uninfected onion sample. For the mycotoxins studied, a good linearity was obtained ( R 2 ≥ 0.99) and the recoveries were in the range of 67–122%, with the highest standard deviation for MON, 22%. The limits of quantification were from 2.5 to 10 ng g −1 in onion matrix. The method was successfully employed for the analysis of mycotoxins in harvested onions showing FBR symptoms and found to be infected with F. oxysporum and F. proliferatum .